How to act when you might be eaten

If you don’t have to worry about reproduction, life gets a little simpler. You have to worry about eating. You have to worry about being eaten. And with that, you’re pretty close to done.

Aspidoscelis uniparens is a parthenogenetic whiptail lizard (formerly Cnemidophorus uniparens), and Eifler and colleagues tested how they allocated their time under threat. To do they, they made six large enclosures (225 square meters) and put in six of these small lizards in. In half of these, they also included two leopard lizards, which prey on the smaller one. In fact, the leopard lizards successfully caught a couple of the subjects during the experiment. Unfortunately, the authors describe the predators in much less detail than the whiptails, which make it a bit difficult to interpret their findings.

The whiptails, not surprisingly, act differently when enclosed with the leopard lizards. They spend a less time moving when housed with leopard lizards, and they’re visible less often to human observers. The whiptails also seem to shift their activity more towards the early hours of the morning (say, 7:00 am), seemingly because the leopard lizards’ activity starts to pick up around 8:00 am.

But the whiptails didn’t change their behaviour as much as much as you might think. time spent in vegetation? Time spent digging? How fast the whiptails move? No differences between the control enclosures and the predator encloses. These are small animals, only a few centimeters long, in a very big, natural enclosure with lots of places to hide. There’s not really any way to predict how “worried” the whiptails would have to be – that is, how strong the predator cues would have to be – for them to start changing their behaviour more dramatically, or to even start changing them at all.

Reference

Eifler, D., Eifler, M., & Harris, B. (2007). Foraging under the risk of predation in desert grassland whiptail lizards (Aspidoscelis uniparens) Journal of Ethology, 26 (2), 219-223 DOI: 10.1007/s10164-007-0053-0